ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...

Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.

Thum.io - A real-time website screenshot generator

Shutter - Shutter is a feature-rich screenshot program.

Blink - Blink is a team and employee app, with a Feed, Chat and Hub (for documents, links, files).

Snipping Tool - Use Snipping Tool to capture a screen shot, or snip, of any object on your screen, and then annotate, save, or share the image